This invention relates to a water jet propulsion unit and more particularly to an improved watercraft powered by a jet propulsion unit.
Jet propulsion units are achieving great popularity as the propulsion unit for watercraft. The jet propulsion unit has many advantages in that it permits the operation in a shallow body of water and also, when concealed within the hull, provides a very neat watercraft appearance. However and particularly when mounted within the hull of the watercraft, there are some disadvantages with jet propulsion units. That is, if the jet propulsion unit is mounted in a fixed position within the hull, then its water inlet will always be submerged even when the watercraft is not in use. Incrustation can build up on the water jet propulsion unit under these circumstances.
To avoid these problems, it has been proposed to provide a water jet propulsion unit of the type wherein the jet propulsion unit is mounted for movement within the hull between a lowered in the water operative position and a raised storage position wherein the water inlet portion of the jet propulsion unit is raised above the body of water in which the watercraft is operating. One convenient way in which this may be done is to mount the jet propulsion unit for pivotal movement about a transversely extending horizontal axis within a tunnel of the watercraft. Such an arrangement is shown in the co-pending application of the same title, Ser. No. 735,154, filed Jul. 22, 1991 in the name of Noboru Kobayashi, which application is a continuation of his earlier application, Ser. No. 489,361, filed Mar. 6, 1990 and now abandoned, which applications are assigned to the assignee hereof.
In accordance with the arrangement shown in that application, it is the normal practice to provide a water inlet opening in the lower portion of the hull of the watercraft which cooperates with the water inlet opening of the jet propulsion unit to direct water from the body of water in which the watercraft is operating into the jet propulsion unit. It is desirable provide mating sealing surfaces between the jet propulsion unit water inlet portion and the hull around its water inlet opening to improve the efficiency of the jet propulsion unit. With the prior art type of constructions, these sealing surfaces have generally been horizontally disposed in a plane generally parallel to but spaced from the pivot axis of the jet propulsion unit. This means that the seal between these surfaces is disposed in such a way that uneven sealing pressures are exerted when the jet propulsion unit is moved to its normal operative position. There are, obvious disadvantages with such an arrangement.
It is, therefore, a principal object to this invention to provide an improved sealing structure between the hull of a watercraft and the water inlet portion of a jet propulsion unit that is pivotally supported within the hull so as to improve the sealing arrangement and maintain uniform sealing pressure around the periphery of the water inlet.
It is a further object to this invention to provide an improved sealing arrangement for the moveable jet propulsion unit of a watercraft.
One way in which the sealing pressure can be made more uniform is to provide the mating sealing surfaces to lie in a plane that is angularly disposed and upwardly inclined so as to intersect and contain the axis of pivotal movement of the jet propulsion unit. It is, however, also desireable to provide a screen across the water inlet opening of the jet propulsion unit to prevent the ingestion of foreign materials such as seaweed or the like. However, when the water inlet opening is angularly disposed and a screen is incorporated, then the angularly disposition of the opening can cause pockets wherein foreign material can accumulate and build up.
It is, therefore, a still further object to this invention to provide an improved water inlet configuration for a jet propulsion unit wherein an angularly disposed screen is incorporated but wherein the build of foreign material on the screen will be precluded.
In addition or in leu of the pivotal movement about the transverse horizontally extending axis, it has also been proposed to support the jet propulsion unit for rotation about a generally longitudinally extending axis so that the water inlet opening may be rotated from a downwardly facing position to an upwardly facing position. In addition to raising the water inlet opening out of the body of water in which the watercraft is operating, this type of support also facilitates access of the water inlet opening through an access opening of the hull for servicing and removing foreign material from the water inlet opening. However, where such rotational support is incorporated, it must be insured that the rotational movement is such that there will not be interference between the water inlet portion of the jet propulsion unit and the hull. This can become a particular problem when the water inlet opening is disposed at an angle to the horizontal so as to improve the sealing, as aforenoted.
It is, therefore, a further object to this invention to provide a water inlet configuration for a jet propulsion unit that will facilitate rotational movement of the jet propulsion unit with minimum interference.